par to stl conversion seems to be a matter of export of 3D models between one of the possible 'part' files to STL format, typically for the purpose of 3D printing. Numerous formats use .par or .part extension, so it might be more than one such conversion exist, but usually export of .par files from Solid Edge is what is actually desired. If you do not have access to SolidEdge, you might need to rely on some 3rd party converter.
Updated: July 28, 2023